WO2008088804A1

WO2008088804A1 - Genetic analyses predictive of asthma

Info

Publication number: WO2008088804A1
Application number: PCT/US2008/000524
Authority: WO
Inventors: Scott Weiss; Marco Ramoni; Blanca Himes
Original assignee: The Brigham And Women's Hospital, Inc.
Priority date: 2007-01-17
Filing date: 2008-01-16
Publication date: 2008-07-24
Also published as: US20090325811A1; US8357517B2

Abstract

The present invention is directed to genetic sequence variations that can be used to predict whether a person will develop asthma. Disease is likely to occur if certain polymorphic forms the CCL11 gene, the CCL2 gene and the TLR7 gene are present.

Description

Genetic Analyses Predictive of Asthma

Cross Reference to Related Applications

The present application claims priority to, and the benefit of, United States provisional application 60/880,709, filed on January 17, 2007, the contents of which is hereby incorporated by reference in its entirety.

Statement of Government Funding

The United States Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others under reasonable terms as provided for by the terms of NIH Grant No. HL067664, awarded by the Department of Health and Human Services.

Field of the Invention The present invention is directed to genetic assays for predicting if a subject will develop asthma. Individuals with a combination of certain polymorphic forms of the CCLl 1 gene, the CCL2 gene and TLR7 gene have a high likelihood of becoming asthmatic.

Background of the Invention Asthma is a complex disease affecting an estimated 20.5 million Americans and costing the US approximately $16.1 billion annually in health care expenses.¹ Models for predicting adult asthma proposed to date have been constructed using clinical characteristics. Measures that have been found to be significant independent predictors include lung function, airway hyperresponsiveness, atopy, parental history of asthma, and female gender.⁵' ⁶ Although a parental history has been found to be a predictor of asthma, ^■ genetic data have not been used to investigate this phenomenon.⁵

Asthma results from the complex interaction of multiple genetic and environmental factors, which causes its phenotypic expression to vary across individuals. In genetic association studies, over 100 genes have been associated with asthma- and atopy-related phenotypes.⁷ Of these genes, 25 have been associated in six or more populations and 54 have been associated in two to five populations. None of the single-gene association studies to date has developed a reliable predictive model of asthma. Because asthma is a prototypical complex disease, traditional association studies, which attempt to find single gene associations or assume an additive model of gene interaction are inherently limited in finding complex genetic interactions that may be predictive of asthma.

Summary of the Invention

The present invention is based upon a novel multivariate method of analysis called Bayesian networks, which are multivariate models able to account for simultaneous associations and interactions among genes to predict asthma status of subjects based on their genotype. Bayesian networks have been successfully used to study gene expression data, protein-protein interactions,⁹ and pedigree analysis.¹⁰ They also have been used to model the multigenic association and predict the occurrence of stroke in sickle cell anemia patients, demonstrating the suitability of such networks for understanding the genetic basis of complex diseases and predicting a clinical phenotype.¹¹ Notwithstanding its recent introduction, the Bayesian network approach is already regarded as an emerging paradigm for the analysis of complex traits.¹²'¹³ Using this approach SNPs were identified that are, in combination, present in patients that are highly susceptible to the development of asthma.

In its first aspect, the invention is directed to a method for diagnostically assessing if a subject is at high risk of developing asthma by determining the polymorphic forms of at least three genes: i) the TLR7 gene (see Figure 1, SEQ ID NO:1); ii) the CCLl 1 gene (see Figure 3, SEQ ID NO:3); and iii) the CCL2 gene (see Figure 5, SEQ ID NO:5). The term "is at high risk" means that the subject is among a group of people where more than 80% will develop asthma. Among the specific single nucleotide polymorphisms that have been, in combination, found to be characteristic of this group are the ones shown in Figure 7. These include: rsl79019 (SEQ ID NO:7); rsl79020 (SEQ ID NO:8); rsl79017 (SEQ ID NO:9); rsl 129844 (SEQ ID NO: 10); rsl7735961 (SEQ ID NO:11); rs4795895 (SEQ ID NO:12); and rs4586 (SEQ ID NO: 13).

The determination of gene sequences may be carried out using any method known in the art. For example, regions of the TLR7, CCLl 1 and CCL2 genes may be amplified using the polymerase chain reaction and then sequenced. Alternatively, a DNA microarray may be used in which oligonucleotides that hybridize to specific polymeric forms of genes under conditions of high stringency (e.g., 0.1-0.5x SSC, 50⁰C - 68°C) are immobilized on a glass, plastic or nylon support. In general, the oligonucleotides should be 20-500 nucleotides in length and should have sequences that hybridize with TLR7, CCLl 1 and CCL2. For example, the microarray may include: a) at least one oligonucleotide with a sequence that matches exactly a corresponding sequence in SEQ ID NO:1 except that one nucleotide is replaced with a different nucleotide, a nucleotide is deleted or a nucleotide is added; b) at least one oligonucleotide with a sequence that matches exactly a corresponding sequence in

SEQ ID NO:3 but in which one nucleotide is replaced with a different nucleotide, a nucleotide is deleted or a nucleotide is added; and c) at least one oligonucleotide has a i sequence that matches exactly a corresponding sequence in SEQ ID NO:5 but in which one nucleotide is replaced with a different nucleotide, a nucleotide is deleted or a nucleotide is added.

In a preferred embodiment the microarray has oligonucleotides that are 20-250 nucleotides in length and there is at least one oligonucleotide that a) has a sequence exactly matching a corresponding sequence in SEQ ID NO:7 and includes the single nucleotide polymorphism of rs 179019; b) has a sequence exactly matching a corresponding sequence in SEQ ID NO:8 and includes the single nucleotide polymorphism of rsl79017; or c) has a sequence exactly matching a corresponding sequence in SEQ ID NO:9 and includes the single nucleotide polymorphism of rs 179017. The microarray may also include at least one oligonucleotide that: a) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 10 and includes the single nucleotide polymorphism of rsl 12944; b) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 11 and includes the single nucleotide polymorphism of rsl7735961; or c) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 12 and includes the single nucleotide polymorphism of rs4795895. In addition, microarrays may include an oligonucleotide exactly matching a corresponding sequence in SEQ ID NO: 13 and which includes the single nucleotide polymorphism of rs4586.

The invention also encompasses kits for amplifying nucleic acids using the polymerase chain reaction (PCR) in which there are pairs of primers for amplifying regions of the TLR7, CCLl 1 and CCL2 genes. These primer pairs may be designed to specifically amplify regions that can be used to determine if the SNPs shown in Figure 7 are present. Thus, for detecting the form of the TLR7 gene present, a kit may include: a) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO:7 and which lies at least partially 5¹ to the single nucleotide polymorphism of rs 179019 and a second that has a sequence exactly matching a sequence in SEQ ID NO: 7 and which lies at least partially 3' to the single nucleotide polymorphism of rsl79019; b) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO:8 and which lies at least partially 5' to the single nucleotide polymorphism of rs 179020 and a second primer with a sequence exactly matching a sequence in SEQ ID NO:8 and which lies at least partially 3' to the single nucleotide polymorphism of rs 179020; and/or c) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO:9 and which lies at least partially 5' to the single nucleotide polymorphism of rs 179017 and a second primer that has a sequence exactly matching a sequence in SEQ ID NO:9 and which lies at least partially 3' to the single nucleotide polymorphism of rs 179017.

The kit may also include primer pairs for detecting the polymorphic form of the CCLI l gene such as: a) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO: 10 and which lies at least partially 5' to the single nucleotide polymorphism of rsl 129844 and a second primer has a sequence exactly matching a sequence in SEQ ID NO: 10 and which lies at least partially 3' to the single nucleotide polymorphism of rsl 129844; b) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO: 11 and which lies at least partially 5' to the single nucleotide polymorphism of rsl7735961 and a second primer that has a sequence exactly matching a sequence in SEQ ID NO: 11 and which lies at least partially 3' to the single nucleotide polymorphism of rsl7735961; and/or c) an oligonucleotide primer pair where one primer has a sequence exactly matching a sequence in SEQ ID NO: 12 and which lies at least partially 5' to the single nucleotide polymorphism of rs4795895 and a second primer has a sequence exactly matching a sequence in SEQ ID NO: 12 and which lies at least partially 3' to the single nucleotide polymorphism of rs4795895. The kit can also include primers that amplify regions of the CCL2 gene which may have polymorphisms. For example, it may have a pair of primers where one has a sequence exactly matching a sequence in SEQ ID NO: 13 and which lies at least partially 5' to the single nucleotide polymorphism of rs4586 and a second has a sequence exactly matching a sequence in SEQ ID NO: 13 and which lies at least partially 3' to the single nucleotide polymorphism of rs4586. In all cases, the primers should be at least 14 nucleotides in length and, in general not longer than about 100 or 200 nucleotides in total.

An association between nucleic acid sequences and the likelihood of developing asthma may also be made at the protein level. Thus, a determination may be made as to whether a subject is at high risk of developing asthma based upon the amino acid sequence of at least: i)the TLR7 gene product (SEQ ID NO:2); ii) the CCLl 1 gene product (SEQ ID

NO:4); and iii) the CCL2 gene product (SEQ ID NO:6). Analysis may be carried out using any method known in the art but immunoassays utilizing antibodies capable of detecting different forms of proteins are generally preferred. The assays may take the form of

ELISAs, radioimmunoassay or arrays in which antibodies or proteins are immobilized on a plate, or slide. Techniques such as SELDI-MS (surface enhanced laser desorption/ionization mass spectrometry) may also prove useful.

Brief Description of the Drawings

Figure 1 : Human TLR7 Reference Nucleotide Sequence. The sequence shown in the figure is designated herein as SEQ ID NO: 1.

Figure 2: Human TLR7 Gene Product. The amino acid sequence shown in the figure is designated herein as SEQ ID NO:2.

Figure 3: Human CCLI l Reference Nucleotide Sequence. The sequence shown in the figure is designated herein as SEQ ID NO:3.

Figure 4: Human CCLl 1 Gene Product. The amino acid sequence shown in the figure is designated herein as SEQ ID NO:4.

Figure 5: Human CCL2 Reference Nucleotide Sequence. The sequence shown in the figure is designated herein as SEQ ID NO:5.

Figure 6: Human CCL2 Gene Product. The amino acid sequence shown in the figure is designated herein as SEQ ID NO:6. Figure 7: Seven SNPs Characteristic of Asthma: The sequences shown in the figure have the following sequence identifiers:

TLR7: rsl79019: SEQ ID NO:7 rsl 79020: SEQ ID NO:8 rsl 79017: SEQ ID NO:9

CCLI l : rsl 129844: SEQ ID NO: 10 ral7735961 : SEQ ID NO: 11 rs4795895: SEQ ID NO: 12 CCL2 rs4586 SEQ ID NO:13

Description of the Invention

The present invention is based upon an association between sequence variations occurring in a combination of three genes and the subsequent development of asthma, hi particular, the genes are the human TLR7 gene (Gene ID 51284, see NCBI sequence NM_016562 and NP_057646, see also, Morris, et al, FASEB J. 20(12) :2153-2155 (2006)); the human CCLl 1 gene (Gene ID 6356, see NCBI sequence NM 002986 and NP 002977, see also, Mir, et al, Parasite Immunol. 2^:397-400 (2006)); and CCL2 (see NCBI sequence NM 002982 and NP 002973, see also, Lee, et al, J. Gen. Virol. 87φtl 2):3623-3630 (2006)).

Methods for genotyping individuals to determine the forms of TLR7, CCLl 1 and CCL2 present are well established in the art. Typically these methods involve a step in which relevant sequences are amplified by PCR. The "Examples" section below provides guidance concerning appropriate procedures but it will be recognized by those of skill in the art that alternatives can also be used. All of the gene sequences required for selecting primers are known and reagents for performing amplifications are commercially available.

Microarrays may also be used in looking for new SNPs and in detecting those that have already been associated with the development of asthma. New SNPs may be looked for by immobilizing sequences that match the known sequences for TLR7, CCLl 1 and CCL2 but in which a single nucleotide is altered. Hybridizations carried out under conditions of high stringency (low salt, e.g., 0.1-0.5x SSC, and high temperature , e.g., 50⁰C - 68°C) may then be used to determine whether a corresponding sequence exists in a sample. Correlations between different polymorphisms and the subsequent development of asthma may then be arrived at using the methodology described herein. Plates with oligonucleotides hybridizing to one or more (preferably all) of the seven SNPs described as being associated with asthma herein may also be used and will be of particular value. Samples that indicate that the TLR7, CCLl 1 and CCL2 genes all have one of the SNPs are an indication that the subject from which they are derived is at very high risk for developing asthma.

The findings presented herein suggest that other alterations in TLR7, CCLI l and CCL2, i.e., beyond the seven SNPs shown in figure 7 may also lead to an increased risk of developing asthma. As discussed above, these changes may be determined using analyses of nucleic acids. However, an examination of the proteins made by these genes, both in terms of amino acid sequence and the amount of protein produced, may also be useful.

The identification of individuals likely to develop asthma may lead to earlier diagnosis, earlier treatment and to counseling regarding life style. In addition, the identification of specific genes that together lead to asthma may suggest new areas for research into the causes and treatment of this disease.

Examples

The present example describes the construction of a Bayesian network using genotypic data from cases with asthma and non-asthmatic controls from the Nurses' Health

Study (NHS), one of the largest prospective studies of risk factors for major chronic diseases in women,¹⁴ that effectively predicts asthma status in subjects from two independent populations.

I. Methods

Training Study

DNA was obtained from incident cases of adult asthma (n=428) and non-asthmatic controls (n=422) from the NHS. Cases were white female lifelong nonsmoking adults with a new self-reported physician diagnosis of asthma, and age-matched controls were white female lifelong nonsmoking adults who did not have a self-reported physician diagnosis of asthma or other pulmonary disease. Self-reported health outcomes in the NHS, including asthma, have been found to be reliable indicators of true disease¹⁵.

Independent Study 1 DNA samples from 21 white asthmatic individuals (16 male, 5 female) were obtained from the Environmental Medicine Genome Bank (EMGB), a repository consisting of army recruits from across the country undergoing basic training. DNA samples from 44 apparently healthy and unrelated self-reported European American (n=21; 10 male, 11 female) and African American (n=23; 11 male, 12 female) adults were obtained from the Coriell Institute for Medical Research (Camden, NJ). Independent Study 2

DNA samples were obtained from 168 unrelated adults originally recruited for an asthma medication trial in the United States. Subjects were 80 male and 88 female white non-smoking asthmatic patients, who were diagnosed according to American Thoracic Society criteria.¹⁶ Asthma diagnosis was confirmed by reversible airway obstruction (of at least 15 percent) by beta-agonists or methacholine challenge testing. The percent predicted FEVl values of all patients were 40 to 85 percent of normal after at least eight hours without inhaling beta-agonists. Further details about this population have been published previously.¹⁷ An independent cohort of 69 controls was collected from the NHS solely for the predictive validation of the model built from the training study. These controls were white female lifelong nonsmoking adults who did not have a self-reported physician diagnosis of asthma or other pulmonary disease.

Informed consent was obtained from all participants. The study was approved by the Institutional Review Board of the Brigham and Women's Hospital.

Genotypinp

Sixty-six candidate genes were identified as likely to be involved in asthma susceptibility by the Innate Immunity in Heart, Lung, and Blood Disease Programs for Genomic Applications (IIPGA).¹⁹ Single nucleotide polymorphism (SNP) selection was performed such that a small set of tagging SNPs distinguished the common haplotypes of the genes of interest. Haplotypes were inferred using the Bayesian method implemented in PHASE, and SNPs that distinguished the most common haplotypes were identified using the BEST algorithm.²¹ Rare SNPs (minor allele frequency less than five percent) were considered for genotyping if the SNP led to a nonconservative amino acid change, implying potential functional significance. Genotyping of the haplotype tagging SNPs (htSNPs) and the nonsynonymous SNPs was performed in the NHS subjects using either multiplexed single-base extension with a Sequenom Mass Spectrometry MALDI-TOF system (SEQUENOM, San Diego, CA) or Taqman real-time PCR with an ABI Prism 7900 machine (Applied Biosystems, Foster City, CA). Approximately 10 percent of samples were genotyped twice as part of standard quality control procedures.

The seven SNPs that were associated with asthma status in our predictive model were then genotyped using either of the above techniques (Sequenom or Taqman) in the EMGB, Coriell, Sepracor, and independent NHS control subjects to provide independent model validation.

Predictive Model Construction

Following the method proposed by Sebastiani et al.,^u a Bayesian network was constructed from a set of 850 subjects (428 cases, 422 controls) genotyped at 226 SNPs in 66 genes using Bayesware Discoverer (http://bayesware.com), a computer program that implements a common Bayesian approach to identify the most probable network of dependency from a dataset.²² To find such a network, the program explores a space of different network models, scores each model by its posterior probability given the data, and returns the model with maximum posterior probability.

Predictive Validation The predictive validation of the model built with the training study was assessed by predicting asthma status in each subject of the two independent studies and comparing the predicted risk of asthma to the actual diagnosis of the subject. The probability of asthma given the genotype of an individual subject was calculated using the clique algorithm implemented in Bayesware Discoverer as described previously. ' ' The performance of the predictive model was evaluated by calculating receiver operator characteristic (ROC) curves. Convex hulls were estimated for each ROC curve using the Qhull algorithm²³ as implemented in Matlab (Mathworks, Natick, MA). The area under the ROC curve convex hull (AURC) was obtained using the trapezoidal rule.²⁴ The predictive accuracy of the network derived from the original 850 NHS subjects was tested with two independent study populations: (1) EMGB asthma cases (n=21) and Coriell controls (n=44), and (2) Sepracor asthma cases (n=168) and NHS controls (n=69).

II. Results

A Bayesian network was created from SNPs from 66 genes genotyped in 850 NHS subjects (428 asthma cases, 422 controls). The network found that seven SNPs in the TLR7, CCLI l, and CCL2 genes modulate the risk of asthma. Of these SNPs, four have a direct effect on asthma status (CCLl l_005208/rs3744508, TLR7_007154/rsl79019, CCLl l_004654/rsl7735961, and TLR7_007042/rs 179020), and three are indirectly associated through the others (CCLl 1 003760/rs4795895, CCL2_005972/rs4586, and TLR7_010982/rsl79017). CCLI l and TLR7 are the two genes that are directly related to asthma status. CCL2 is related to asthma status through CCLl 1. Remaining SNPs that were linked to one another in separate networks mostly correspond to SNPs of the same gene. No TLR7, CCLl 1 , or CCL2 SNPs were linked to SNPs of other genes and one TLR7 SNP was not linked to any other node in the network.

The accuracy of this seven-SNP network was tested by using it to predict asthma status in two independent adult populations. The first group, consisting of 21 cases with asthma and 44 controls, was very well differentiated into cases and controls and had an AURC of 0.95. The second independent population, consisting of 168 cases with asthma and 69 controls, was well differentiated into cases and controls by the network with an AURC of 0.82. Although the initial model was constructed using data from females only, tests on the independent study populations, which included male and female cases and controls and black and white controls, were still effective in differentiating cases from controls.

The fundamental role of epistatic interactions was assessed by comparing the ability of each individual SNP to predict asthma to that of using all SNPs. Our results show that these SNPs individually fail to accurately predict asthma status, as demonstrated by the corresponding AURC values of 0.5, the predictive accuracy achieved by random chance.

The two SNPs that are nearest the asthma status node in the network have a slightly increased accuracy, but this accuracy is far lower than that resulting from using data of all seven SNPs.

III. Discussion The present example demonstrates that a multivariate SNP model effectively predicts asthma status in subjects from two independent populations. A predictive model was constructed from genotypic data from white female NHS data, which found that seven SNPs from three genes out of 226 SNPs from 66 genes modulate the risk of asthma. The predictive ability of this model was tested on two independent study populations, including both male and female subjects and black and white controls. These results show that our predictive model is accurate in subjects of either gender and is robust to some measure of racial variability.

The CCLI l and TLR7 genes, which are directly related to asthma status in our model, are known to have a role in asthma-related phenotypes. The product of the CCLl 1 gene, eotaxin, is a C-C chemokine involved in the recruitment of peripheral blood eosinophils into the lung during acute allergic inflammation,²⁵ has been found at high levels in bronchoalveolar lavage fluid of asthmatic individuals,²⁶ and is correlated with asthma severity²⁷ and airway hyperresponsiveness.²⁸ TLR7 is a toll-like receptor (TLR) that specifically recognizes viral single-stranded RNA.²⁹ The activation of TLRs leads to the activation of cytokines and other genes that mediate immune responses.³⁰ Consistent with the involvement of TLR7 in asthma, a study of mice treated with a TLR7 ligand prevented allergen-induced airway hyperresponsiveness and eosinophilia, and led to decreased IgE levels.³¹ The Bayesian network suggests a biological mechanism by which both TLR7 and CCLl 1 mediate asthma. Based on what is known about both genes, one possible hypothesis is that viral infection with rhinoviruses, common single stranded RNA viruses that are frequently associated with asthma exacerbations in adults,³² may stimulate TLR7 to activate an eosinophilic inflammatory response that is mediated by CCLl 1.

We are not aware of any published study to date that has reported on the association of TLR7 variants with asthma or a related phenotype. Previous studies have investigated the association of individual CCLl 1 variants with asthma and found discrepant results. A recent family-based study found that one CCLl 1 SNP is associated with asthma among black subjects, and other CLLI l variants are associated with IgE levels among black and white subjects.³³ However, five case-control studies have found no association between CCLl 1 variants and asthma,^34"38 although some of these studies did find an association with related phenotypes.³⁶'³⁸ The inconsistency among the results of these single-SNP association studies may be due to the inadequacy of traditional analytic measures to find associations when a gene variant has a biological effect in the context of other genes. Multivariate methods able to account for the interactions underpinning complex biological processes, such as the one used in this example, increase the ability to find association of SNPs to a phenotype because effects that are modulated through complex interactions can be found.

ROC curve analysis suggested that, in the first independent population, a predictive model based upon the sequences discussed above is ideally sensitive (100 percent) and highly specific (84 percent) at its most accurate threshold. By comparison, ROC curve analysis for the second independent population, suggested the model is highly sensitive (95/90/87 percent) for thresholds at which the specificity is lower (54/57/60 percent).

References

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Claims

What is Claimed is:

1. A method of assessing if a subject is at high risk of developing asthma, comprising: a) determining the polymorphic form of at least three genes: i) the TLR7 gene (SEQ ID NO: 1 ); ii) the CCLl 1 gene (SEQ ID NO:3); and iii) the CCL2 gene (SEQ ID NO:5); b) correlating the frequency of combinations of polymorphic forms with the likelihood said subject is at high risk of developing asthma.

2. The method of claim 1, wherein it is concluded that said subject is at high risk of developing asthma if said subject: a) has a TLR7 gene with a sequence characterized by the single nucleotide polymorphism of: rsl79019 (SEQ ID NO:7); rsl79020 (SEQ ID NO:8); or rsl79017 (SEQ ID NO:9); b) has a CCLl 1 gene characterized by the single nucleotide polymorphism of: rsl 129844 (SEQ ID NO: 10); rsl7735961 (SEQ ID NO:11); rs4795895 (SEQ ID NO: 12); and c) has a CCL2 gene characterized by the single nucleotide polymorphism of rs4586 (SEQ ID NO: 13).

3. The method of claim 2, wherein said TLR7 gene is characterized by the single nucleotide polymorphism of: rsl79019 (SEQ ID NO:7).

4. The method of claim 2, wherein said TLR7 gene is characterized by the single nucleotide polymorphism of: rsl 79020 (SEQ ID NO:8).

5. The method of claim 2, wherein said TLR7 gene is characterized by the single nucleotide polymorphism of: rsl 79017 (SEQ ID NO:9).

6. The method of any one of claims 2-5, wherein said CCLl 1 gene is characterized by the single nucleotide polymorphism of: rsl 129844 (SEQ ID NO:10).

7. The method of any one of claims 2-5, wherein said CCLl 1 gene is characterized by the single nucleotide polymorphism of: rs 17735961 (SEQ ID NO:11).

8. The method of any one of claims 2-5, wherein said CCLl 1 gene is characterized by the single nucleotide polymorphism of: rs4795895 (SEQ ID NO: 12).

9. A method of assessing if a subject is at high risk of developing asthma, comprising: a) determining the amino acid sequence of at least three polypeptides: i) the TLR7 gene product (SEQ ID NO:2); ii) the CCLl 1 gene product (SEQ ID NO:4); and iii) the CCL2 gene product (SEQ ID NO:6); b) correlating the frequency of combinations of polymorphic forms of the proteins with the likelihood said subject is at high risk of developing asthma.

10. A DNA microarray for detecting the presence of SNPs indicative of a subject being at high risk of developing asthma, comprising oligonucleotides immobilized on a glass, plastic or nylon support, wherein said oligonucleotides are 20-500 nucleotides in length and wherein: a) at least one oligonucleotide has a sequence that matches exactly a corresponding sequence in SEQ ID NO:1 but in which one nucleotide in said corresponding sequence is replaced with a different nucleotide; b) at least one oligonucleotide has a sequence that matches exactly a corresponding sequence in SEQ ID NO:3 but in which one nucleotide in said corresponding sequence is replaced with a different nucleotide; and c) at least one oligonucleotide has a sequence that matches exactly a corresponding sequence in SEQ ID NO: 5 but in which one nucleotide in said corresponding sequence is replaced with a different nucleotide.

11. A DNA microarray for detecting the presence of SNPs indicative of a subject being at high risk of developing asthma, comprising oligonucleotides that are immobilized on a glass, plastic or nylon support, wherein said oligonucleotides are 20-250 nucleotides in length and wherein at least one oligonucleotide: a) has a sequence exactly matching a corresponding sequence in SEQ ID NO:7 and includes the single nucleotide polymorphism of rsl79019; b) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 8 and includes the single nucleotide polymorphism of rs 179017; or c) has a sequence exactly matching a corresponding sequence in SEQ ID NO:9 and includes the single nucleotide polymorphism of rsl79017.

12. The DNA microarray of claim 1 1, further comprising at least one oligonucleotide that: a) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 10 and includes the single nucleotide polymorphism of rsl 12944; b) has a sequence exactly matching a corresponding sequence in SEQ ID NO:11 and includes the single nucleotide polymorphism of rsl7735961; or c) has a sequence exactly matching a corresponding sequence in SEQ ID NO: 12 and includes the single nucleotide polymorphism of rs4795895.

13. The DNA microarray of either claim 11 or claim 12, further comprising an oligonucleotide exactly matching a corresponding sequence in SEQ ID NO: 13 and includes the single nucleotide polymorphism of rs4586.

14. A kit for amplifying nucleic acids using the polymerase chain reaction (PCR) comprising: a) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 7 and which lies at least partially 5' to the single nucleotide polymorphism of rsl 79019 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 7 and which lies at least partially 3' to the single nucleotide polymorphism of rsl 79019; b) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO:8 and which lies at least partially 5' to the single nucleotide polymorphism of rsl 79020 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO:8 and which lies at least partially 3' to the single nucleotide polymorphism of rsl79020; and/or

c) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO:9 and which lies at least partially 5¹ to the single nucleotide polymorphism of rs 179017 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO:9 and which lies at least partially 3' to the single nucleotide polymorphism of rs 179017.

15. The kit of claim 14, further comprising: a) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 10 and which lies at least partially 5' to the single nucleotide polymorphism of rs 1129844 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 10 and which lies at least partially 3' to the single nucleotide polymorphism of rsl 129844;

b) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 11 and which lies at least partially 5' to the single nucleotide polymorphism of rsl 7735961 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 11 and which lies at least partially 3' to the single nucleotide polymorphism of rsl 7735961; and/or

c) an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 12 and which lies at least partially 5' to the single nucleotide polymorphism of rs4795895 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 12 and which lies at least partially 3' to the single nucleotide polymorphism of rs4795895.

16. The kit of either claim 14 or 15, further comprising an oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 13 and which lies at least partially 5' to the single nucleotide polymorphism of rs4586 and a second oligonucleotide primer at least 14 nucleotides in length and that has a sequence exactly matching a sequence in SEQ ID NO: 13 and which lies at least partially 3' to the single nucleotide polymorphism of rs4586.

17. The method of either claim 1 or 2, wherein said polymorphic forms are detected by PCR amplification of nucleic acid derived from said subject followed by sequence analysis of the amplified DNA.